Three-dimensional metal printing of inclined walls and conic geometries through a WAAM system with optimized mobility and torch control: metallographic and mechanical characterization
摘要
This research work exposes the metal printing of complex shapes with the wire arc additive manufacture (WAAM) achieved thanks to the optimized control and mobility of the welding torch (multiple degrees of freedom addition). The mobility optimization was accomplished through a 3D printer redesign using stepper motors, mobility rails, and an adaptable control for different types of gas metal arc welding (GMAW) torches. The above allowed for the printing of walls with different inclination angles (0°, 15°, and 30°), cantilevers, and concentric conic shapes without collapse. The proposed 3D printer design reduced the cost of the torch holder without losing accuracy and keeping a high metal deposition rate. The microstructure and mechanical properties (microhardness) of conic and inclined walls fabricated with a stainless-steel wire grade 308L were assessed. The heat dissipation varied with the layer location, its inclination level, and the change in the wetting angle between layers. Coarsen columnar dendritic microstructures with delta ferrite traces were generated in the walls due to the high cooling rates, reducing the layer microhardness. In contrast, the low cooling rates and the thermal gradient between internal and external layers promoted an annealing effect in the conic geometries. Consequently, microstructures composed of refined and coarse grains were formed. The microhardness decreased in granular microstructures but maintained a higher uniformity level in both types of WAAM builds (cantilever and concentric conic geometries).